Ahead of the curve

Alvar Aalto was the kinder, gentler face of modernism - the man who put Finland on the architectural map, and made saunas his speciality. Fiona MacCarthy recalls a shared lunch of smoked reindeer and schnapps in his elegant Helsinki restaurant

Why use a straight line when you can make a curving one? Alvar Aalto's buildings have an undulating force. The walkways curl around them. The rooflines curve and soar. Even Aalto's famous vases are designed to be things of rippling contours. The Finnish 20th-century modernist architect was a master of sinuosity. If Mies van der Rohe was the high priest of angularity, Aalto was his opposite. It is Aalto's predilection for these lyrical, organic forms and natural materials that suits our current mood.

How very Finnish Aalto was. He was not, a friend once wrote, an "architect for all men". Unlike some other international modernists, Aalto was not a man with a suitcase ready packed. Of the 500 or so architectural projects of his lifetime, 400 were buildings for his native land. When he taught and built abroad, most notably in America, it seems he always hastened to return to that remote and sparsely populated country of enveloping dark winters and magical, bright summers. He was always obsessed by the quality of light.

Born in 1898 in a small rural village in southern Ostrobothnia, his father a surveyor, his grandfather a forester, Aalto kept his deep feeling for that endless Finnish landscape of forests and lakes. As an architect, what moved him was not just the lie of the land, but its practical geology. He saw building as a matter of "grappling with the very matter yielded to us by the earth's crust".

The Finland of Aalto's background was exactly that described so wonderfully in Helen Dunmore's recent novel House of Orphans: the tensions of the turn of the 19th century, the growing resistance to the Russian rule over a largely Swedish-speaking population. Finland, then a Grand Duchy of the Russian empire, did not achieve independence until 1917. Aalto inherited many of the values of the surge of nationalistic culture that overtook Finland during this unsettled period: Sibelius's music, Gallen-Kallela's paintings, Lars Sonck and Eliel Saarinen's architecture. He saw his role as architect and city planner in utopian terms, as the creation of a Finnish "earthly paradise", taking up the title of William Morris's poem. But, aesthetically, he found the "dream of the north" movement, with its emphasis on folklore and historicism, stifling: too many quasi-medieval inglenooks. His vision was much simpler and more pure.

The building that brought Aalto international recognition was the Paimio tuberculosis sanatorium, a high, white, clean-lined building in the pine forests near Turku, designed in 1929. At that time, Finns were dying from the disease at a rate of 100 a week. He conceived the building as "an instrument of healing", a beautiful and optimistic place. Having recently been ill himself, he knew that the bedridden were not like other people: supine and not upright, agonised by glaring light, painfully distracted by the noises and draughts from artificial ventilation. His aim was to provide complete peace for the patient, with purpose-designed furniture and lights, and muted colours. This was typical of Aalto's humanist approach.

By the early 1930s, Aalto was emerging as the gentler, less dogmatic face of modernism, providing an alternative to Walter Gropius, Le Corbusier and other architects of the modernist elite. According to the English critic JM Richards, it was at the meetings of the Congrès Internationaux d'Architecture Moderne in 1929 and 1933 that these more doctrinaire architects first became aware of "the new voice from the northern fringe of Europe that was soon to add colour and richness to their somewhat austere vocabulary". Finland at the time was very little visited. Richards went to Paimio and he saw the early stages of Aalto's legendary Viipuri Library. For English architectural enthusiasts, Finland became the new cult country, promised land of sail and sauna. One or two even bought islands in the archipelago.

It is fascinating to watch how Aalto infiltrated an England otherwise so resistant to the modernists, finding them too harsh, high-principled and foreign. What was it about Aalto that made him so immediately acceptable? His lack of pomposity? His practicality? His designs have an element of peasant ingenuity, pragmatic solutions to the problems that present themselves. Aalto arrived like an influx of fresh air in the Tudorbethan England of the early 1930s. The first solo exhibition of his bentwood furniture was held in London and was enthusiastically received. Two oddities about this debut are striking in retrospect: it was held at Fortnum and Mason, Piccadilly, not a store one now associates with cutting-edge design; and Aalto's chief supporter in this country was the writer and bon viveur P Morton Shand. His granddaughter Camilla Parker Bowles later acquired a husband whose views on modern architecture have been made all too widely known.

From 1938, Aalto was designing his opus con amore, the Villa Mairea, a large family house in western Finland. There are just a handful of 20th-century houses in the western world that live on in the memory long after one has left them: Greene and Greene's Gamble House at Pasadena; Charles Rennie Mackintosh's Hill House at Helensburgh; Eileen Gray's house, E1027, built high on the cliffs at Roquebrune; Frank Lloyd Wright's Fallingwater. Aalto's Villa Mairea is one of these.

This deeply romantic and atmospheric house, set on a hilltop with views across the forest to a sawmill in the distance, is both a poem of appreciation for Marie and Harry Gullichsen, the friends and long-term collaborators who commissioned it, and Aalto's hymn to an ideal Finnish way of country life. Marie Gullichsen was herself a painter and art patron, Finland's nearest equivalent to Peggy Guggenheim. The villa, with its spatial harmonies, free forms and multiplicity of textures, is a painterly house - restful but visually very stimulating, expansive but marvellously intimate.

In the 1930s, Aalto's admiration for Japanese art, craft and design grew. He loved its poise and skill and what he saw as its "enormous sensitivity and tact towards the individual". Aalto co-founded the Helsinki Japan Club. That the current Alvar Aalto exhibition at the Barbican has been curated by the Japanese architect Shigeru Ban shows that the connections are still strong. In the Villa Mairea, the Japanese and Finnish elements are fused to remarkable effect. In designing the sauna building, for example, Aalto took as his starting point the Karelian village bathing house and laundry, a homely communal building with turfed roof. He flattens and extends the roofline, paring down the structure to its purest abstract geometry. It is the sort of delicate, meditative building you find on a Kyoto temple site.

Aalto took sauna culture solemnly. He designed at least 30 saunas in his lifetime, both institutional and private. You might call the sauna Aalto's speciality. I remember a long conversation with him once on what one might call its eternal moral values, the emblematic importance of the Finnish national ritual of communal cleansing. To be authentic, the preparations for the sauna needed to be drawn out: an exquisite foreplay of heating up the stove from outside through a hole in the wall. Only an old-fashioned smoke sauna was authentic. Aalto poured scorn on the flick-of-a-switch electrical variety. When, during US-Finnish diplomatic negotiations in the 1960s, it had been suggested that Aalto should design a sauna as a gift for John F Kennedy, he refused to cooperate, suspecting that the president would not treat the sauna with the proper spiritual respect.

"Human life is a combination of tragedy and comedy. The shapes and designs that surround us are the music accompanying this tragedy and this comedy." Finland had endured a singularly tragic sequence of events in the second world war. In 1939, a few months after Aalto completed his sensational Finnish Pavilion for the World's Fair in New York, the Soviet Union invaded Finland, and in the negotiated settlement most of the eastern province of Karelia was ceded to the Russians. By the summer of 1941, the treaty with the Soviet Union had broken down and Finland entered the war on the German side. Aalto, writing in 1957 after these traumatic national vicissitudes, recognised the way in which buildings, like music, register and amplify the emotions of the times. His postwar buildings are his war requiem. His architecture entered a distinct new phase.

In Aalto's so-called "red period", the immediate postwar years, his Romantic imagination flourished. These refulgent red-brick buildings with their pitched copper roofs stood in total contrast to the tall glass buildings, such as Skidmore, Owings and Merrill's Lever House, and Mies van der Rohe's Seagram Building, which were then de rigueur on the international scene. Aalto's steadfast red-brick structures, constructed in local materials, connect visibly with their natural environment. To the British, with our own fine tradition of brick building, the parallels are with the Kentish oast house or the medieval keep. These are children's storybook buildings, comprehensible and lovable, except that they are enormously sophisticated.

Säynätsalo Town Hall, the lecture theatre at Otaniemi Technical University, the Helsinki National Pensions Institute - Aalto's postwar practice produced poetic buildings, replete with memory and history, and they were of great importance, psychological as much as physical, in the rebuilding of Finland after the ravages of war. With its beautiful façade of red brick, copper and grey granite, the National Pensions Institute was internationally admired. It was envisaged as a part of the city, an assembly space, a modern equivalent of the Roman forum. The skylit interiors are uplifting. Perhaps only Aalto could have made a pensions office into a building of such sensuous delight.

By the time I met him in the mid-1960s he was no longer the outsider from the north, but accepted on the international scene as an architectural superstar on the level of Le Corbusier, Mies van der Rohe, Walter Gropius and Frank Lloyd Wright. He had by then built his own Ronchamp, the Lutheran Church of the Three Crosses at Vuoksenniska. In Finland, Aalto was the king, and there was a kind of twinkliness of manner with which he both accepted and refuted such acclaim.

He received me in his purpose-designed office at Munkkiniemi in Helsinki, into which he had moved quite recently. Until then, he had always had his studio within the house where he lived. Even here, the office had a familial feel, with Elissa, Aalto's considerably younger second wife, in attendance and smiling. His first wife, Aino, had been an architect as well. The two-storey studio-office had been built within a courtyard that contained a small-scale amphitheatre structure. Aalto was a great lover of Greece, and the splayed-out form, the fan shape of the ancient theatres, was one of his recurring themes.

Aalto's lifetime spanned a mass migration of the Finns from the country to the cities. One of his preoccupations at the time I met him was how one could arrive at a modern expression of civic pride. He walked me around the giant model of his plan for the Töölö Bay area of Helsinki: lake, park and concert hall, a museum of architecture, art gallery and library, a building for the Academy of Finland. Of this vision of the fusion of nature and national culture, only the white marble Finlandia Hall was completed as he planned it. But Aalto's concept of informal modern monumentalism, our lasting need for celebratory and ruminative buildings, has been influential. The British Library, for instance, Colin St John Wilson's St Pancras masterpiece, is very Aalto-esque.

Aalto took me to lunch at the Savoy, the elegantly luxurious Helsinki restaurant he designed in 1937, another of his love poems to his patron, Marie Gullichsen. It was for the Savoy restaurant that Aalto's now iconic Savoy vase was first designed. Smoked reindeer tongue was on the menu and, as I remember, a lot of schnapps was drunk. Aalto talked with some emotion about Viipuri Library, one of his seminal early buildings which had disappeared with the Russian occupation and was believed to have been destroyed.

Its rediscovery in the late 1980s, neglected but not irrevocably damaged, was for Aalto admirers a little miracle. Gradually, in a delicate matter of cooperation between the Finns and Russians, the building is being carefully restored. The spectacularly undulating timber ceiling in the lecture hall, removed by the Russians, has now been reconstructed. It is sad to think that Aalto, who died in 1976, will never know it exists once more. He profoundly understood the transitory nature of global architecture - how, in a war-torn landscape, the buildings come and go.

· Alvar Aalto: Through the Eyes of Shigeru Ban is at the Barbican, London EC1, until May 13. Details: 0845 120 7500